The present invention relates generally to a balancing arrangement for rotating machines, especially turbomachines. In rotating machines, an interior space of a housing of the machines is typically at a higher or lower pressure relative to the atmosphere. The present invention relates more particularly to a balancing arrangement for a rotating machine having a housing which is provided with covers for openings to be used during assembly and maintenance of the machines and where one or more balancing weights are provided for the rotating members.
The housings of large machines having rotatable members, especially of turbomachines, generally have either a positive and/or negative pressure with respect to the surrounding atmosphere both during operation of the machines and when the machines are about to operate. When such machine, or respectively the rotor of such machine, requires balancing or rebalancing, the covers of the housing openings which provide access to the rotor must be removed. Accordingly, a communication is established between the atmospheric pressure surrounding the machinery and the positive and/or negative pressure within the housing. This communication will interrupt the operating conditions within the machine housing, and may result in a loss of costly gas fillings. Consequently, extensive delays in the restarting of the machine must oftentimes be accepted. For example, hydrogen is often used for gas fillings, especially in the case of gas-cooled generators, and due to its nature will be lost upon the opening of the housing.
In the case of known balancing arrangements, the balancing of rotors in assembled machines is being achieved by having the balancing weights both installed and secured in bores that are provided for this purpose within the rotors. However, the weights can be installed only by opening up the housing of the rotating machinery, for example of a turbomachine or a generator.
It is an object of the present invention to provide a balancing arrangement whereby a rebalancing of a rotor becomes possible either without equalizing a gas filling or a positive or negative pressure existing in the machine housing with the surrounding atmospheric pressure, or respectively without the escape of the gas filling, present inside the housing, into the atmosphere.
In the present invention a movable screw-in pressure lock having a male thread is provided in a cover of a housing of machinery for the purpose of maintaining a difference in pressure in the housing of the machinery relative to the atmosphere during a rebalancing of a rotor.
It will be particularly advantageous to arrange a sealing cover at the pressure lock to seal the pressure lock with respect to the surrounding atmosphere. Furthermore, it is advantageous to provide a sealing surface for the pressure lock with the sealing surface to be urged into contact with the rotor.
The arrangement of the present invention has a particular advantage in that the installation of a pipe with a male thread, constructed as a pressure lock, into each individual cover of the housing and the placement of a mechanically fastened seal against the atmosphere at the contact areas of the cover will allow a rebalancing of the rotor in a simple manner without any communication either of the positive or negative pressure or of the gas filling within the machine housing with the surrounding atmosphere. By means of this arrangement and for the purpose of balancing the rotor, the pipe serving as the pressure lock is screwed into the housing until a tube end of the pressure lock carrying the sealing surface and facing the balancing plane at the rotor makes contact with a machined surface of a balancing plane of the rotor. The sealing cover which is provided on the pressure lock on the side of the surrounding atmosphere is then removed, and it then becomes possible to install the appropriate balance weights in the rotor by the use of suitable tools. The weights are installed through the pressure lock existing between the outer atmosphere and the higher and/or lower pressure area in the housing without disturbing the state of pressure existing within the housing.
It is still further advantageous in the present invention to provide a sealing safety hood for the pressure lock to protect the pressure lock during operation of the rotatable member.
The arrangement of a safety hood covering an entrance opening of the pressure lock will prevent any unintentional opening of the pressure lock even in the event of an unscheduled and careless handling of the covers.